The present invention relates to nonwoven fabrics, and to methods for fabric fabricating nonwoven fabrics. In particular, the present invention relates to a method for forming laminate nonwoven that is flushable and biodegradable.
Wipes and other industrial and sanitary nonwoven fabrics are known. These fabrics may be used for wiping liquids or moist solids. Often, it is desirable for one side of the fabric to remain substantially dry when the other is exposed to the liquid or moist solid. To accomplish this, a substantially impermeable fabric layer may be used, or multiple layers of permeable layer may be bound together with adhesive. These wipes may comprise normal tissue, wet laid tissue, and spunlace fabrics. These fabrics may be used in various combinations in a laminate with an adhesive binder.
These types of wipes, however, are disadvantageous in that they are not flushable. The fabric qualities that render them substantially impermeable to a liquid penetration also render them as disadvantageously non-degradable in the sewer system. For commercial success, flushable wipes generally must have four properties: 1) be stable during use with liquids/moist solids, 2) must lose integrity in the sewer system under normal shear forces, 3) be biodegradable, and 4) have a soft surface feel.
U.S. Pat. No. 5,935,880 to Wang, et al., discloses a wipe that satisfies the previously mentioned four properties, however, a binder is incorporated on at least one side of the wipe and the wipe is exposed to full face hydraulic needling. The application of a binder, which in the Wang patent is a composition of three different ingredients, adds to cost complexity and production time, while utilizing a full face hydraulic entanglement process consumes more energy due to the increased number of water jets needed to uniformly entangle the full width of the fabric. These two factors make for a wipe that is neither cost effective nor energy efficient.
There is thus a heretofore unresolved need in industry for a method for making a nonwoven fabric that is flushable and biodegradable, cost effective, and energy efficient.
In a first embodiment of the method for making a laminate nonwoven fabric of the invention, the method comprises the steps of: providing a first nonwoven layer on a moving support; providing a second nonwoven layer overlying the first layer on the moving support; and pattern hydroentangling the first and second layers to one another to form a laminate nonwoven fabric. The step of pattern hydroentangling the first and second layers comprises providing a first manifold with a plurality of jet cluster therein, each of the jet cluster having a plurality of individual jet orifices therein, with the jet orifices each separated from one another by at least a first distance. The jet clusters are separated from one another by a second distance that is greater than the first distance. Preferably, the second distance is at least twice the first distance, and more preferably at least 10 times the first distance. The first embodiment of the method of the invention further comprises the step of conveying the second layer overlying the first layer on the moving support under the manifold in a machine direction while directing streams of water through each of the individual jet orifices onto the underlying nonwoven layers, with the layers thereby entangled with one another.
Because the jet orifices are organized into separated and distinct jet clusters, the resulting entanglement pattern is not xe2x80x9cuniformxe2x80x9d across the cross direction of the laminate, but is instead along substantially linear lines in the machine direction. The resulting laminate is characterized by strongly bundled areas, with weakly unbundled areas therebetween. These weak unbundled areas are engineered to allow the laminate to lose its integrity under the shear forces in the sewage systems.
A second embodiment of the method for making a laminate nonwoven fabric of the invention comprises the steps of: providing a first nonwoven layer on a moving support; providing a second nonwoven layer overlying the first layer on the moving support; and pattern hydroentangling the first and second layers to one another to form a laminate nonwoven fabric. The step of pattern hydroentangling the first and second layers comprises providing a first manifold with a plurality of jet orifices therein separated form one another by a distance, and conveying the second layer overlying the first layer on the moving support under the manifold in a machine direction while moving the manifold in a direction coincident with the machine direction. Streams of water form each of the individual jet orifices will be directed onto the first and second layers to thereby laminate them to one another, with the areas of lamination not linear in the machine direction due to movement of the manifold. Preferably, the manifold is oscillated in a substantially cross direction to create a xe2x80x9cwavyxe2x80x9d entanglement pattern in the laminate.
In an additional embodiment of the method of the invention, at least a second manifold is provided also having a plurality of water jet orifices therein. As the overlaid first and second nonwoven layers are conveyed beneath the moving first manifold and the second manifold, the layers are hydroentangled with a substantially linear pattern by the stationary second manifold and a non-linear pattern by the moving first manifold. In a further embodiment of the method of the invention, the second manifold is also moved in a direction coincident with the machine direction to thereby enhance the non-linear entanglement pattern. Preferably, the first and second manifolds are oscillated in substantially opposite direction to create a zig-zagged entanglement pattern.
It will be appreciated that altering the number and movement of the manifolds used to hydroentangle the nonwoven layers within the scope of the invention can result in an almost limitless variation of entanglement patterns.
Preferably, the first manifold has a plurality of jet clusters therein, with each of the jet clusters having a plurality of individual jet orifices; each of the jet orifices within each of the jet clusters separated from one another by a first distance, and with each of the jet clusters separated from one another by a second distance that is greater than the first distanced. Preferably, the second distance that separated jet cluster is at least twice the first distance that separates individual jet orifices within each cluster. More preferably, the second distance is at least 10 times the first distance. Also, the second manifold preferably has its individual jet orifices arranged into jet clusters.
In still an additional embodiment of the method of the invention, three layers and laminated to one another, with the first and third preferably comprising thin veneer layers, and the second and center layer comprising a tissue or pulp layer.
It has been discovered that through the method of the invention, a laminate nonwoven fabric may be made that solves the above discussed heretofore unresolved problems in the art. In particular, the novel method of pattern hydroentangling using manifolds with spaced clusters of jets results in a laminate fabric that holds together sufficiently for use, both that is otherwise not so tightly bound so as to be degradable under the normal sheer pressures present in the sewer system.
The above brief description sets forth rather broadly the more important features of the present disclosure so that the detailed description that follows may be better understood, and so the present contributions to the art may be better appreciated. There are, of course, additional features of the disclosure that will be described hereinafter which will form the subject matter of the claims appended hereto. In this respect, before explaining the several embodiments of the disclosure in detail, it is to be understood that the disclosure is not limited in its application to the details of the construction and the arrangements set forth in the following description or illustrated in the drawings. The present invention is capable of other embodiment and of being practiced and carried out in various ways, as will be appreciated by those skilled in the art. Also, it is to be understood that the phraseology and terminology employed herein are for description and not limitation.